Some viruses, such as papilloma viruses (e.g., HPV16, HPV18), retroviruses (e.g., HTLV, feline leukemia virus), herpes viruses (e.g., Epstein Barr Virus), and hepatitis viruses (e.g., HBV), are known to cause cancer in humans and other animals. While vaccines, which utilize viral coat proteins or virus-like particles, are often successful at preventing infection, there is a need for therapies that treat established disease and virally-associated cancers.